徐州市7株猪链球菌病原学分析及分子分型研究

目的 对2020-2022年徐州市3起人感染猪链球菌疫情中分离到的7株猪链球菌进行鉴定和分型,了解本地区猪链球菌的病原学特征和流行特点。方法 采集与病例相关猪的鼻拭子和外环境等标本进行猪链球菌分离,采用飞行质谱和VITEK-2 Compact等微生物鉴定系统进行鉴定,对分离到的猪链球菌进行血清型、毒力基因的检测,并通过多位点序列分型(MLST)和脉冲场凝胶电泳(PFGE)等方法进行分子分型和溯源分析。结果 6株猪链球菌为血清2型,其中2021年人源(1株)与猪源(3株)猪链球菌荚膜多糖基因(cps2J)、溶菌酶释放蛋白基因(mrp)、细胞外蛋白因子基因(ef)和溶血素基因(sly)检测均为阳性,多位点序列分型结果为ST7型,PFGE同源性为100%,推断人可能因宰杀带菌猪时通过破损的伤口而感染;2020年和2022年临床分离株mrp基因缺失,多位点序列分型结果为ST1型。2022年外环境分离菌株不携带4种所检测的毒力基因,非数据库中已知ST型别。结论 本地区分离到的猪链球菌株携带多种毒力基因,致病菌株主要为血清2型,ST1和ST7型。

Pathogenic analysis and molecular subtyping of seven Streptococcus suis strains in Xuzhou

Three outbreaks of human infection with Streptococcus suis in Xuzhou occurred from 2020 to 2022. Epidemiological investigations were performed, and pig nasal swabs and environmental specimens were collected for Streptococcus suis isolation. A total of seven strains of Streptococcus suis were isolated. A time of flight mass spectrometer and VITEK-2 Compact microbial analysis systems were used for identification. The serotype and virulence genes of Streptococcus suis were detected. Multilocus sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) were used for molecular typing and traceability analysis, to reveal the pathogenic characteristics and epidemic characteristics of Streptococcus suis in Xuzhou. Six strains of Streptococcus suis were of serotype 2. The virulence genes of Streptococcus suis from human (one strain) and pig (three strains) sources were cps2J+/mrp+/ef+/sly+, and the MLST results indicated ST7 type. The homology of PFGE was 100%. Human infection by Streptococcus suis was inferred to be caused by broken wounds in people slaughtering infected pigs. The mrp gene of human strains in 2020 and 2022 was deleted, and the MLST results indicated ST1 type. The strain isolated from environmental samples in 2022 did not carry the four virulence genes, and the MLST type was not known, according to the database.